1. Field of the Invention
The present invention relates to an image forming system which has a reproduction factor automatic selection mode for automatically setting a reproduction factor and a paper size automatic selection mode for automatically selecting a paper size, and which can automatically form an optimal image in accordance with a size of each of original.
2. Description of the Prior Art
In one conventional copying machine, a transfer paper of a size optimal for an intended copying operation is automatically selected in accordance with a detected original size and a preset reproduction factor. In another conventional copying machine, a reproduction factor is automatically preset in accordance with a detected original size and a detected paper size. In accordance with automatic copying operation performed in a conventional copying machine of this type, normally, two parameters are selected from three parameter, i.e., an original size, a transfer paper size and a reproduction factor (or a magnification factor), so as to uniquely determine the remaining one parameter. An automatic copying operation is performed in accordance with the three parameters determined in this manner. For example, when the user sets an original, designates a paper size and selects the reproduction factor automatic selection mode, the reproduction factor is automatically calculated and proper copying operation can be performed irrespective of the original size. When the user sets an original, designates a reproduction factor and selects the paper size automatic selection mode, paper of a proper size is automatically selected. For this reason, a desired copy can be obtained even if the operator does not have any knowledge as to the paper size and reproduction factor.
However, the operator may erroneously set both the paper size automatic selection mode and the reproduction factor automatic selection mode. The operator may also set a paper size even if he has already selected the paper size automatic selection mode.
As described above, in a copying machine having the reproduction factor automatic selection mode or the paper size automatic selection mode, the operation procedure on the side of the operator is simplified, and almost no error occurs in the copying operation. For example, when a need arises for copying an image of A3 size on a paper having A4 size or when an image of A3 must be reduced in half, the required reproduction factor or the required cassette (in this case A4R) can be automatically selected and the operator need not know why such reproduction factor or cassette is required.
However, due to limits in the number of combinations available from a single type of machine, some specific copying operations cannot be performed. For example, when an original image of B5 size is to be copied with a reproduction factor of 50% or less, the copying operation cannot be performed unless the machine has a cassette of a size smaller than B5 size mounted thereon. When an image of A3 size is to be reproduced on paper having A5 size, the copying operation cannot be performed if the machine allows setting of reproduction factor exceeding only 50%.